Copending application Ser. No. 830,979, filed Sept. 6, 1977, by Robert F. Johnson and assigned to the assignee of the present invention, discloses and claims means for laser trimming active semiconductor devices. In particular, it is shown how a pair of junction field effect transistor (JFET) devices can be laser trimmed so as to balance their performance. This is important because a very useful class of semiconductor monolithic integrated circuit operational amplifiers (op amps) has been developed. In this circuit form, the useful characteristics of JFET devices have been combined with those of bipolar junction transistor (BJT) devices to provide op amps of extremely useful performance. In one instance, a JFET input stage having very high input impedance is used to drive a BJT output stage. Typically, the input stage is biased by JFET devices as shown in U.S. Pat. No. 3,959,733 which issued to James E. Solomon and Ronald W. Russell on May 25, 1976, and is assigned to the assignee of the present invention.
JFET devices are difficult to manufacture to a precise balance and, when used in the above-described balanced circuitry, are often provided with external offset adjustment means. More recently, the above-described laser trimming has been applied and has eliminated the need for external adjustment in many cases. However, the laser trimming operation is tedious and slow, and requires great care in its implementation. It would be highly desirable to perform the trimming on a mass production basis.